Add the linux,spidev compatible in spidev
Several device in ramips have this binding in the dts

Signed-off-by: Giuseppe Lippolis <giu.lippolis@gmail.com>
---
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -695,6 +695,7 @@ static struct class *spidev_class;
 static const struct of_device_id spidev_dt_ids[] = {
 	{ .compatible = "rohm,dh2228fv" },
 	{ .compatible = "lineartechnology,ltc2488" },
+	{ .compatible = "siliconlabs,si3210" },
 	{},
 };
 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
